In the filling, handling and dispensing of hollow containers, it is necessary that the containers be of uniform size and shape in order that high-speed filling and handling machinery can be used. If the outer diameter of the finish of the container is not between a predetermined maximum and minimum value, the closure for capping the container will either not fit over the lip of the finish or will fit over the lip of the finish without fitting snugly thereon. It is, therefore, important to reject containers during manufacture which vary from the predetermined standard size and shape. In the distant past, this has been accomplished primarily by visual inspection. Such an inspection, of course, is subject to human error and, therefore, is not entirely satisfactory.
To eliminate the human error associated with the visual inspection, a cup gauge was developed to reject containers wherein the outer diameter of the lip of the finish is not between a predetermined maximum and minimum value. The cup gauge is a device having a cup with an inner diameter corresponding to the maximum diameter mounted at one end and a cup with an inner diameter corresponding to a minimum diameter mounted on the other end. An inspector uses the cup gauge to test each container by insuring that the cup of maximum diameter fits over each and every container, i.e., a GO test, and that the cup of minimum diameter does not fit over any of the containers, i.e., a NO-GO test. If the cup of maximum diameter does not fit over the container or if the cup of minimum diameter does fit over the container, that container is rejected. Such an inspection, of course, still requires an inspector and actual physical contact with each and every one of the containers.
Automatic gauging equipment is presently available that eliminates the need for an inspector. However, the equipment still accomplishes gauging by contact with the finish which can be chipped as a result of such contact. Devices have been developed to accomplish gauging without physical contact such as, for example, U.S. Pat. No. 3,245,531 granted to B. B. Mathias et al and assigned to the assignee of the present invention. However, such devices required a complex arrangement of optics and mechanisms to provide an analog signal having a temporal profile proportional to the shape of the containers. These analog devices are costly, generally unreliable because of a lack of sufficient resolution, and unable to provide measurements at now-standard high production rates.